Mobile wireless communication systems, for example cellular telephony or private mobile radio communication systems, typically provide for radio telecommunication links to be arranged between a plurality of user or subscriber terminals, often termed ‘mobile stations’, MSs, via a system infrastructure including one or more base transceiver stations (BTSs).
Many of these systems utilize duplex (two-way communication) paths which can be arranged in a frequency division duplex (FDD) configuration, whereby a frequency is dedicated for uplink communication, i.e. from a MS to its serving BTS, and a second frequency is dedicated for downlink communication, i.e. from a serving BTS to one or more MSs. Alternatively, the paths can be arranged in a time division duplex (TDD) configuration, whereby a first time period is dedicated for up-link communication and a second time period is dedicated for downlink communication.
An example of a mobile wireless communication system is a TETRA (TErrestrial Trunked RAdio) system, which is a system operating according to TETRA standards or protocols as defined by the European Telecommunications Standards Institute (ETSI). A primary focus for a TETRA system is use by the emergency services, as TETRA provides efficient dispatch and control services. The system infrastructure in a TETRA system is generally referred to as a switching and management infrastructure (SwMI), which contains substantially all of the communication elements apart from the MSs.
The communication system may provide radio communications between the infrastructure and MSs (or between MSs via the infrastructure) of information in any of the known forms in which such communications are possible. In particular, information may represent speech, sound, data, picture or video information. Data information is usually digital information representing written words, numbers etc, i.e. the type of user information processed in a personal computer, often referred to in relation to communication in a network as ‘text’ information or ‘packet data’ information. In addition, control signalling messages are communicated. These are messages relating to the communication system itself, e.g. to control the manner in which user information is communicated in compliance with the selected industry protocol such as TETRA. Different channels may be used for communication of the different forms of information. In particular, control channels are used for transmission of control signals, and packet data channels (PDCHs) are used to provide packet data units (PDUs) in which packet data information is sent to or from MSs.
Packet data Units (PDUs) include besides user data, information such as type, source/destination user id, size, etc and are used for processing and controlling data communication according to the specified standard. The transmission of PDUs is typically based on priority. The prioritization between PDUs makes it possible to achieve the required Quality of Service (QoS) in the system. The QoS is mainly defined by two parameters, throughput and processing delay. The requirements of the QoS depend on the application type and can also be imposed by the protocols in the standard. However, it is possible for PDUs having lower priority to end up being completely excluded by higher priority PDUs. It can also be difficult to efficiently control transmission with PDUs of varying priorities and sizes. While Class Based Weighted Fair Queuing (CBWFQ) has been utilized for wired link transmission, the wired link transmission does not face issues with capacity or efficiency that can be seen in a wireless link environment.
Accordingly, there is a need to improve the scheduling of PDUs so that message transmission occurs in an efficient and controllable manner particularly in a wireless link environment, especially with the latest tendency to move from circuit-switched approaches for the voice traffic to a fully packet-switched model as is the case for 3GGP Long Term Evolution (LTE).
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments. In addition, the description and drawings do not necessarily require the order illustrated. Apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the various embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments.